Perez, 21, was stung at the Amarillo airport and was later hospitalized for five days in September. Her head swelled to twice its normal size and she needed a skin graft to rebuild the ear that had rotted from necrosis.

The Daily Mail sounded an alarm about a University of Kansas study by graduate student Erin Saupe, saying the "deadly" spider was "spreading ... to a town near you."

The spider's habitat is limited to the Southeast and Midwest, stretching from Kansas east to the Appalachian states.

But Saupe of the university's Geology and Biodiversity
Institute used computer modeling to predict how it's habitat might move north to states such as Wisconsin, Michigan, Pennsylvania and even New York, dependent on climatic suitability for the species.

But Rick Vetter, the nation's foremost expert on the brown recluse spider -- loxosceles reclusa -- said such media reports use "scare tactics," and 90 percent of the time a bite causes nothing more than a red mark on the skin.

"These are distorted reports ... hyperbolic media crap," said Vetter, a research associate in the department of entomology at the University of California-Riverside.

A Kansas home, for instance, was infested with 2,055 brown recluse spiders for a period of 17 years and "not one" in the family of four was bitten, according to one of his studies, published in the Journal of Medical Entomology.

He said gnarly photos of Perez's injuries looked authentic and he had known a 9-year-old who had lost an ear from necrosis. But such cases are rare.

The spider's venom -- sphingomyelinase D -- induces red blood cell destruction. Symptoms can include pain at the site of the bite, itching, muscle and joint pain, as well as vomiting and fever.

"My crusade is to stop stupidity in the medical community," Vetter said.

When doctors blame a skin lesion on the brown recluse, they might overlook other more serious conditions such as methicillin-resistant staphylococcus aureus (MRSA), diabetes or even lymphoma.

In a 2005 article he co-wrote in the New England Journal of Medicine, Vetter cited 40 other conditions that can cause necrosis often misdiagnosed as a spider bite.

Vetter was so tired of doctors blaming the much-maligned spider, he started the Brown Recluse Challenge. Of 1,800 specimens sent to him, only 350 turned out to be the real deal. And all were from the Midwest.

A brown recluse bite can be life-threatening in 10 percent of the cases, but Vetter estimates there are only one or two deaths a year, typically in small children.

Brown Recluse Spiders Could Head North

Vetter worked with Saupe on her master's project, in which she tracked the spiders' predicted migration through "ecological niche modeling."

She used two models to predict the spider's range in 2020, 2050 and 2080, given the effects of global warming, concluding they might move north but those left behind would die off.

Kansas is a "hotbed" for these spiders, said Saupe, who has predicted that they might become extinct in the southern portions of their range by 2080 as the climate in their natural habitats becomes to warm and their mobility is restricted.

Most are reclusive, as their name suggests, and go nowhere near humans. Those that are threatened can bite, but often with just a "dry bite" that does not emit venom, Saupe said.

It is dormant part of the year, which means bites usually occur from April until October. They tend to come out at night and hide under bedding and clothes, in dark places.

Still, the spiders can be lethal.

ABCNews.com reported in 2010 on Victoria Franklin of Marietta, Ga., who had surgery to remove a necrotic breast after a brown recluse bite.

Franklin, 51, still has kidney and other medical problems related to the bite.

"I have no medical insurance at all," she told ABCNews.com in an email. "Medication is also expensive. I have nine different medications that I have to take every day, sometime twice a day."

Saupe's study co-author, Paul Selden, said the species was "the commonest spider in my house" in Lawrence, where the paleontologist and arachnologist teaches at the University
of Kansas Paleontological Institute.

"They are in the bathroom under my sink in the cupboard," said Selden, a professor of invertebrate paleontology, or fossil spiders. "The problem is you leave a towel on the floor and it will scurry under there. In the morning, you pick up the towel and it may be on it."

At first, her parents thought a red, quarter-sized lesion on her thigh was a boil, but when red lines began to crawl up her leg, they knew it was more serious.

"I remember getting injections into the site and I still ended up losing quite a bit of flesh," she said. "I still have a divot on my thigh.

"I have always been creeped out by spiders," Hardesty added. "I still shake out my clothes and my husband shakes his shoes out. I tell the kids [19 and 16] to check the bed before they crawl in if it's been dormant for a week or so.